T-bolt and pad for liner mounting

ABSTRACT

A cylindrical grinding mill shell with liner segments maintained in operable position by bolts extending through slots in the segments and openings in the shell with nuts threadable engaging the bolts at the outer ends thereof abutting the outer wall of the shell. Pad members of polytetrafluorethylene are positioned between each bolthead and corresponding mating surface of each segment. The pad members have a very desirable plastic memory, good absorption for vibration effects, a high resistance to temperature distortion and destruction and provide a certain lubricity which facilitates subsequent disassembly.

United States Patent [72] Inventor Robert N. Heighberger Moreland Hills, Ohio 746,647

July 22, 1968 June 1, 1971 Joseph Dyson & Sons,1nc. Eastlake, Ohio [21] Appl. No. [22] Filed [45] Patented [73] Assignee [54] T-BOLT AND PAD FOR LINER MOUNTING 3 Claims, 6 Drawing Figs.

[52] 11.8. C1. 241/183 [51] Int. Cl B02c 17/22 [50] Field of Search 241/182,

183, 299, 300; 85/50, 1 (JP); l51/38;287/101(Cursory);

30/267(Cursory) [56] References Cited UNITED STATES PATENTS 851,013 241/183 4/1907 Lohnert 1,315,025 9/1919 Lawler 241/183 1,591,938 7/1926 Harrison.. 241/183 3,231,301 1/1966 Gray 287/101 3,298,270 1/1967 Launay 85/50X Primary Examiner-Dona1d G. Kelly Attorney-Robb & Robb ABSTRACT: A cylindrical grinding mill shell with liner segments maintained in operable position by bolts extending through slots in the segments and openings in the shell with nuts threadable engaging the bolts at the outer ends thereof abutting the outer wall of the shell. Pad members of polytetrafluorethylene are positioned between each bolthead and corresponding mating surface of each segment. The pad members have a very desirable plastic memory, good absorption for vibration effects, a high resistance to temperature distortion and destruction and provide a certain lubricity which facilitates subsequent disassembly.

Fig.2

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1 T-BOLT AND PAD FOR LINER MOUNTING The invention is particularly directed to a means for insulating in effect the means for connecting the liners to the shell of the mill mounted for axial rotation, this shell being generally cylindrical and the invention resides in the material from which the means are constructed and the method of installing the same and incorporating the means into the actual connecting devices for fastening mill liners therewithin.

A particular object of the invention is to provide means for fastening liner segments within the shell of a grinding or crushing mill so that the bolts usually availed of for that purpose do not receive as much unloosening effect as would be the case in mills of other construction which do not avail of the invention, and particularly the use of polytetrafluorethylene as a dampening agent in conjunction with the fasteners availed of and the installing of segments, is a substantial improvement since it eliminates a great deal of labor of periodic tightening of the segment fastening bolts, and in fact makes it possible to remove the segments when the liners are worn as ultimately takes place.

Another particular object of the invention is to provide for installing the liners by provision of bolts which are generally called T-bolts; the material which is provided in this instance as an important part of the invention, namely polytetrafluorethylene being used as a pad underneath the head of the T-bolt for separating the pressure surface of the T- bolt from the surface against which the same would normally be drawn upon rotation and tightening action of the nut, so that subsequently in use, the vibration and resonance effect imparted to the liner segment are not in fact transmitted into an unloosening tendency of the bolts which are used for fastening such segments to the shell of the mill or the like.

A further particular object of the invention is to provide the pad or insulating means in such a form that it may be used in the conventionally and presently constructed mills in conjunction with the liner segments and bolts availed of therein, to be inserted under the head of the bolt and drawn down into a cavity, between the respective pressure surfaces by which the liner segments are retained in place, providing such pad material in a suitable thickness as will produce the necessary separation of such surfaces, that is the pressure surfacesand at the same time, by reason of the characteristics of the material, increase the effective tightening action which is exerted thereagainst because of the tendency of the material to assume its original condition and form.

Other and further objects of the invention will be understood from a consideration of the specification appended hereto, and shown in the drawings wherein:

FIG. 1 is an enlarged fragmentary sectional view showing the portion of the outer shell housing of a typical mill in which the installation of this invention is incorporated, and liners in place therewithin indicating the general relationship of the respective pad, bolt, liner and shell.

FIG. 2 is an enlarged fragmentary view, illustrating in further detail the shape of a bolt and certain physical aspects thereof.

FIG. 3 is an enlarged fragmentary view, about on the line 33 of FIG. 2, looking in the direction of the arrows, further illustrating certain critical characteristics of a typical bolt in somewhat exaggerated form.

FIG. 4 is a fragmentary view, taken about on the line 4-4 of FIG. 2, looking in the direction of the arrows.

FIG. 5 is a plan view of the pad used in conjunction with the bolt for the purposes hereof.

FIG. 6 is a side view of the pad, shown in FIG. 5.

Referring now to FIG. 1, the mill which is known as a crushing or grinding mill is usually provided in generally cylindrical form and includes a housing suggested at 1, which is of relatively thick metal, and is adapted to have mounted at the inner surface 2 thereof and along such inner surface, a series of segments 3 which are of conventional form and well known in the art, extending axially with respect to the shell 1, that is along the axis and being of sufficient width to span the shell from end to end, such segments 3 being symmetrical as will be understood with respect to bolt openings such as 4 provided, these being drilled or bored through the liner material, and such liners or segments being of suitable metallic form to resist wear as much as possible, there usually being at least two or three such openings 4, extending along parallel to the axis, to receive bolts such as 5 indicated in FIG. I, as being emplaced in the openings 4. 7

It is pointed out that the segments 3 will be duplicated throughout the entire inner periphery of the cylindrical shell 1 and against the face 2 thereof so as to provide a wear surface which may be replaced if necessary as wear takes place, this being a necessary result of the grinding or milling operation to which the mill is subjected.

The bolt 5 as shown herein, is a somewhat conventional bolt having the threads 6 at theone end and a sort of T-shaped head 7 at the other end.

The head 7 is more particularly shown in FIGS. 2, 3 and 4, and may best be described as being a segment of a conical portion wherein the surfaces such as 8 are flat opposite one another, and the surfaces 9 developed of what remains of the conical portions of the generally conically shaped head 7.

A suitable nut 10 is mounted on the threads 6, and adapted in normal and conventional mill construction to-draw the T- head 7 into a mating opening ill formed in the liner segment 3, there being an opening of this nature for each bolt positioned along parallel to the axis aswill be understood.

The FIGS. 2, 3 and 4 are referred to at this point, being enlarged and somewhat exaggerated so as to indicate that the surface 9 incorporates therein by reason of the fact that the bolts are usually formed by forging or similar other forming process, to thus have a large number of high spots which may be denoted l2, representing a sort of imperfect surface which is produced during the actual manufacture of such bolts 5, as by upsetting the forging or other means where no machine is resorted to form such surface, but the same is substantially as it is formed without further grinding or other machine operation being performed thereon.

It will be appreciated that the opening in each of the liner segments 3, denoted 111, is formed so as to mate with such T- head, and thus is in effect an elongated slot in which the surface such as M is of similar unmachined configuration usually with the liner segment 3, for example, is cast although the opening or bolthole 4 therewithin is probably usually or may be drilled or otherwise machined thereinto and through.

It will thus be seen that where ordinary mill construction is resorted to and mounting of the liner segments 3 therewithin, in normal application the bolt head 7 would be drawn down into the elongated slot II with metal-to-metal contact of the surface 9 thereon with the surface 14 formed in such slot.

In the instant invention however, there is provided a pad as indicated in FIG. 5 for example, and denoted 15, which may be simply provided as a rectangular member in which an opening 16 is pierced to provide for locating the pad 15 on the bolt 5 in about the position shown in FIG. I initially, wherein the pad 15 lies between the respective surfaces 14 and 9, these surfaces being denoted pressure surfaces for the sake of concise description.

This pad 15 is preferably formed of polytetrafluorethylene, to take advantage of the characteristics of such material which are to have very desirable plastic memory, good absorption, resistance to temperature distortion and destruction, and a certain lubricity which facilitates subsequent disassembly where necessary, the material being sufficiently resilient to enable torquing of the nut 10 sufficiently to maintain the liner segments 3 in position and yet to permit subsequent disassembly, the pad 15 being interposed between the pressure surfaces so that the imperfections 12 on the surface 9 will not contact those of the elongated slot 11, and thus set up a resonant vibration when the mill is being operated.

It is important to note that the polytetrafluorethylene has been found to be particularly superior in the arrangement disclosed, and whereas formerly it was often necessary to actually resort to metal-cutting torches to remove the bolts and segments, with the contemplation hereof, the nuts such as may be backed off in a generally conventional fashion, and the liner segments replaced when wear has reached a point requiring such replacement.

It should also be noted that the pad provides a sealing effect since it is slightly wider than the slot in which the head 7 of the bolt 5 is positioned, and thereby additionally furnishes a sealing effect when a wet process of milling or grinding is resorted to.

The elastic memory of polytetrafluorethylene is such that it seeks to return to its original shape and volume, and thus additionally adds to the fastening tightness which may be resorted to and which thus increases the advantage of using the material hereof.

It is of course to be understood that whereas the pad is shown as being rectangular and preferably so, at the same time it may be that other forms can be resorted to under certain circumstances.

I claim:

1. ln grinding mill construction of the class described, in combination, a shell of generally cylindrical configuration, mounted for axial rotation, liner means comprising removable segments positioned within said shell, and means to maintain said segments in operable position, including elongated slots in the segments, said slots being connected with openings through the segments, openings through the shell aligned with said segments openings, bolts having heads conforming to the slots aforesaid, and seated therein, threads on the opposite ends of said bolts extending beyond the outer surface of the shell, nuts engaging said threads, and pad members of polytetrafluorethylene positioned along at least a major portion of each bolt head and between the pressure surface thereof and the mating pressure surface of the slot in which said head is seated, whereby to conform to the contour of said head and slot and prevent said pressure surfaces from coming into direct contact with each other.

2. The combination as claimed in claim 1 wherein the pad members are formed of substantially rectangular pieces of polytetrafluorethylene of sufficient thickness to absorb vibrations tending to loosen the bolts after the same are torqued, and maintain the opposed pressure surfaces in spaced relationship.

3. The combination as claimed in claim 1 wherein the pad members are formed of polytetrafluorethylene of an area such that pressure surfaces normally engaging one another are maintained in spaced relationship and of Sufficient thickness to prevent contact of said surfaces, the loosening tendency resulting from vibrations and resonance being thereby substantially obviated. 

1. In grinding mill construction of the class described, in combination, a shell of generally cylindrical configuration, mounted for axial rotation, liner means comprising removable segments positioned within said shell, and means to maintain said segments in operable position, including elongated slots in the segments, said slots being connected with openings through the segments, openings through the shell aligned with said segments openings, bolts having heads conforming to the slots aforesaid, and seated therein, threads on the opposite ends of said bolts extending beyond the outer surface of the shell, nuts engaging said threads, and pad members of polytetrafluorethylene positioned along at least a major portion of each bolt head and between the pressure surface thereof and the mating pressure surface of the slot in which said head is seated, whereby to conform to the contour of said head and slot and prevent said pressure surfaces from coming into direct contact with each other.
 2. The combination as claimed in claim 1 wherein the pad members are formed of substantially rectangular pieces of polytetrafluorethylene of sufficient thickness to absorb vibrations tending to loosen the bolts after the same are torqued, and maintain the opposed pressure surfaces in spaced relationship.
 3. The combination as claimed in claim 1 wherein the pad members are formed of polytetrafluorethylene of an area such that pressure surfaces normally engaging one another are maintained in spaced relationship and of sufficient thickness to prevent contact of said surfaces, the loosening tendency resulting from vibrations and resonance being thereby substantially obviated. 